Can OpenAI simulations be used in real world applications?
In general, you can use a simulation to prepare and train a controller for a real world application. A good example of this being done for robotics is in the paper Autonomous helicopter flight via reinforcement learning where a Reinforcement Learning agent was trained on a model of helicopter dynamics before being used in reality. Often, as in this case, such work is done to avoid expensive failures due to the trial and error nature of RL - if an error is expensive, such as crashing a helicopter, then ideally the agent performs the checks to avoid it in simulation, by planning or some other virtual environment as opposed to in the real world.

The main hurdle to completing training in simulation then transfering to the real world, is the fidelity of the simulation. The simulation's physics, including measurements of physical quantities, the size of time steps, amount of randomness/noise, should match between the simulation and the target real-world environment. If they do not match, then a learning agent could generate a policy that works in simulation, but that fails in reality.

For the autonomous helicopter, the researchers used data from a human operator controlling the real helicopter, to help generate a predictive model that was used in the simulation. 

Can you do the same with Open AI Gym environments? Probably not, unfortunately. The main issue is that the units used are fixed in most environments, and are unlikely to closely relate to any specific real world implementation of the same kind of system. In addition, the physics is often simplified - probably a minor issue for CartPole, but a more major one for environments like LunarLander which ignores weight of fuel used and is a 2D simulation of a 3D environment.

So, for instance, in CartPole environments, the following values are fixed:


Size of time step
Mass of cart
Mass and length of pole to be balanced
Force that cart motor pushes with


There are a couple of approaches you could use to work around this:


Make a new version of the environment and adjust it so that values match to a real environment you want to train for. Note this may still be limited, as the physics model is still quite simple, and may not allow for the real operating characteristics of the cart motor.
Use the CartPole environment as-is, not to train a controller directly, but to select hyper parameters, such as neural network size, learning rate etc. That will result in a learning agent that you are reasonably confident can learn policies with the state representation and general behaviour of your target system. You then train "for real" again in the physical system.


You can combine these ideas, creating a best-guess controller from simulation, then refining it in a real environment by continuing the training on a real system.